Wildflowers of Toronto's High Park
Ragweed, common
Ambrosia artemisiifolia
Family: Composite/Aster
Annual
Native to Ontario
Blooms: August to October
Habitat: Waste places
Height: up to 1 m
Leaves: fern-like
Female flower heads: single, inconspicuous, in axils of upper leaves.
Male flower heads: Long terminal spike bearing up to 50 florets which produce vast quantities of pollen. This is spread by wind and is a major cause of hay fever.
